Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS FOR PROVIDING CONSTANT TORQUE OUTPUT
FROM A DOOR CLOSER OR OPERATOR
Related Applications
This application claims priority to U.S. Application No. 61/892,674, filed
October
18, 2013.
Technical Field
The present invention is directed to a door closer which provides even
pressure to a
door throughout the range of the door swing.
Description of Related Art
In the door closer/operator industry today there is the need for the user to
feel a
constant force when opening the door, especially on doors needing to meet ADA
requirements. According to the prior art, one solution is a double lever arm
which
changes the vector angle between the arm and the door as the torque increases
on
the door closer/operator due to a linear spring. Another solution is the cam
and
roller design where the cam profile changes with the spring compression to
provide
a constant torque output. Prior art door closers include those of U.S. Patent
No.
4,653,227; U.S. Patent Publication No. 2013/0081227; U.S. Patent No.
4,763,385;
and U.S. Patent No. 8,732,904. Each of these designs has disadvantages. Each
has
mechanical losses due to friction, the rack and pinion setup on the double
lever
arm closers and the cam roller on the cam/roller design. Additionally, they
each
require very strict tolerances for proper functionality.
Disclosure of the Invention
Bearing in mind the problems and deficiencies of the prior art, it is
therefore an
object of the present invention to provide an apparatus and method for
providing a
constant torque to open and close a door.
It is another object of the present invention to provide a door closer and/or
operator
that provides a desired torque profile during the opening and closing of a
door.
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A further object of the invention is to provide a door closer and/or operator
with
constant torque output and improved maintenance and wear characteristics.
Still other objects and advantages of the invention will in part be obvious
and will
in part be apparent from the specification.
__ The above and other objects, which will be apparent to those skilled in the
art, are
achieved in the present invention which is directed to a door closer or
operator
comprising a door closer or operator housing adapted to be mounted to one of a
door frame or a door and a pivoting pinion on the door closer housing for
transmitting door motion between the door closer housing and the other of the
door
__ or door frame. A cam is connected to the pinion and rotatable therewith
about an
axis of rotation, the cam having a peripheral edge about the axis of rotation.
The
door closer further includes a spring having two ends, with a first end
secured to
the door closer housing, and a connecting member secured to the spring
adjacent a
second end thereof to compress the spring. The connecting member extends along
__ the spring from the spring second end to a position beyond the spring first
end
where the connecting member is tangential to and engages the peripheral edge
of
the cam. Rotation of the cam causes a change in length of the portion of the
connecting member between the position tangent to the cam peripheral edge and
the spring second end to expand or compress the spring, resulting in a force
__ transmitted along a longitudinal axis of the connecting member as a result
of spring
deflection. The cam peripheral edge has a profile with a varying radial
distance
between the cam axis and the connecting member at the position tangent to the
cam peripheral edge such that the radial distance is changed as the spring
expands
or compresses to maintain a desired torque about the axis of the cam and the
__ connected pinion.
The profile of the cam peripheral edge may be circular or non-circular, and
have a
radial distance between the cam axis and the connecting member at the position
tangent to the cam peripheral edge such that the radial distance is reduced as
the
spring compresses or expands to provide a desired torque profile about the
axis of
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the cam and the connected pivoting member, such as maintaining a constant
torque
about the axis of the cam and the connected pivoting member.
The cam may have a groove disposed along the peripheral edge of the cam and
the
connecting member may be a cable. The cable has a first end secured to the cam
and a second end secured adjacent the spring second end, with the cable
wrapping
around the cam in the groove as the cam rotates to compress or expand the
spring.
The cam may include teeth about the peripheral edge and the connecting member
may includes teeth engaging the cam teeth. The cam may comprise a pinion with
teeth about the peripheral edge and the connecting member may comprise a rack
with teeth engaging the pinion teeth.
The spring may comprise a coil spring with a central opening and the
connecting
member may extend through the spring central opening from the spring second
end
to the cam.
The door closer or operator may have a linkage arm for pivoting the door
between
open and closed positions, the linkage arm having a first end attached to and
sliding
with respect to a track mounted to the other of the door frame or the door
surface
and a second end secured to the pinion and rotatable therewith. Alternatively,
the
door closer or operator may have a double lever arm for pivoting the door
between
open and closed position, the double lever arm having a first end mounted to
the
other of the door frame or the door surface and a second end secured to the
pinion
and rotatable therewith. The door closer or operator may employ no linkage
arms,
and the door may be secured to the pinion such that the axis of rotation of
the door
becomes the axis of rotation of the pinion.
In a related aspect, the present invention is directed to a method of
controlling
.. operation of a swing door. The method includes providing a door in an open
or
closed position interposed in a door frame and secured to the door frame by at
least
one hinge, and providing a door closer mounted to one of the door frame or the
door surface and having the structure and features described above. The method
includes urging the door into the other of the open or closed position and
rotating
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the pinion and connected cam about the cam axis as the door moves. The
rotation
of the cam causes a change in length of the portion of the connecting member
between the position tangent to the cam peripheral edge and the spring second
end
to expand or compress the spring and transmitting a force along a longitudinal
axis
of the connecting member as a result of degree of compression of the spring.
The
method includes maintaining a desired torque about the axis of the cam and the
connected pinion as the door moves to the other of the open or closed position
as a
result of the changing radial distance of the cam axis to the cam peripheral
edge at
the position tangent to the connecting member as the spring expands or
compresses.
Brief Description of the Drawings
The features of the invention believed to be novel and the elements
characteristic of
the invention are set forth with particularity in the appended claims. The
figures are
for illustration purposes only and are not drawn to scale. The invention
itself,
however, both as to organization and method of operation, may best be
understood
.. by reference to the detailed description which follows taken in conjunction
with the
accompanying drawings in which:
Fig. 1 is a perspective view of a first embodiment of the door closer of the
present
invention employing a single lever arm arrangement mounted on a door partially
opened.
Fig. 2 is a perspective view of the door closer of Fig. 1 with the door more
fully
opened.
Fig. 3 is a top plan view of the interior of the door closer of Fig. 1 showing
an
embodiment of the spring, pinion and variable radius cam of the present
invention.
Fig. 4 is a side elevational view of the door closer interior of Fig. 3.
.. Fig. 5 is a perspective view of an embodiment of the door closer rotating
member
carrying the pinion and cam of the present invention.
Fig. 6 is a perspective view of the cam in Fig. 5.
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Fig. 7 is a perspective, partially cut away view of the back side of the cam
of Fig. 6.
Fig. 8 is a graphical representation of the increasing closing force on a door
using a
constant radius cam.
Fig. 9 is a side cut-away view of an embodiment of the variable radius cam of
the
present invention showing the cable in different relative positions during
closing of
the door.
Fig. 10 is a graphical representation of the constant closing force on a door
achieved using a varying radius cam according to the present invention.
Figs. 11 - 13 are side views of an embodiment of the door closer of the
present
invention employing a geared rack and pinion configuration for the connecting
member and cam, respectively.
Fig. 14 is a top plan view of an embodiment of the door closer of the present
invention in which a double lever arm connecting arrangement is employed.
Fig. 15 is a top plan view of an embodiment of the door closer of the present
invention in which the pinion serves as a hinge for the door.
Mode(s) for Carrying Out Invention
In describing the preferred embodiment of the present invention, reference
will be
made herein to Figs. 1 - 15 of the drawings in which like numerals refer to
like
features of the invention.
The present invention is particularly directed to a door closer or operator
which
provides a constant force on a door regardless of the door position. Unless
otherwise indicated, the term door operator includes door closer, and vice
versa.
One embodiment of the closer includes a pinion, a spring, a cable attaching
spring
to pinion, and a variable radius pulley wherein the cable rides on a variable
radius
.. at the point where the spring force is acting as the pinion rotates during
opening or
closing of the door. The closer may also include a damping component that
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dampens the force from the user applied in the opening direction of the door,
momentum of the door, backcheck, and the force from the spring or momentum of
the door in closing, sweep and latch, and can be done through hydraulic
control,
electrical control, or other conventional methods. Certain terminology is used
herein for convenience only and is not to be taken as a limitation on the
embodiments described. For example, words such as "top", "bottom", "upper,"
"lower," "left," "right," "horizontal," "vertical," "upward," "downward,"
"clockwise"
and "counterclockwise" merely describe the configuration shown in the figures.
Indeed, the referenced components may be oriented in any direction and the
terminology, therefore, should be understood as encompassing such variations
unless specified otherwise. As used herein, the term "open position" for a
door
means a door position other than a closed position, including any position
between
the closed position and a fully open position as limited only by structure
around the
door frame, which can be up to 180 degrees from the closed position.
The attached drawings include Figs. 1 and 2 which shows a door having an
embodiment of the door closer 10 and Figs. 3 and 4 showing the inside
components of the door closer. The door closer 10 is secured to the upper
portion
of an otherwise conventional swing door 80 that is mounted to a door frame 84
with hinges 82 for pivoting movement of the door 80 relative to the frame 84
between a closed position and an open position. For the purpose of this
description, there i is shown only the upper portion of the door 80 and the
door
frame 84 to which the door closer is mounted. The door closer 10 includes a
housing 12, a pivoting pinion 20 extending therefrom, and an operator arm
assembly 14 operably coupling the door closer 10 to the door frame 84. A
horizontally extending track 16 is securely mounted to an upper portion of the
door
frame 84 adjacent the upper edge of the door 80 when closed, and slidingly
receives a roller at end 14b of the single operator linkage arm 14. The other
end
14a of operator arm 14 is mounted to a pinion 20, and rotates therewith. As
door
80 opens and closes, arm 14 rotates relative to door closer 10 and causes
pinion 20
to rotate accordingly. As shown, door closer 10 is mounted on the pull side of
door
80, i.e., the side away from frame 84, and track 16 is mounted above the door,
but
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the door closer may be mounted on the opposite, push side of the door, and the
track mounted below the upper portion of the door frame. Track 16 may also be
mounted to the either side of the wall adjacent to the door frame 84, or
concealed
within the wall or door frame 84. Alternatively, door closer 10 may be mounted
on
the door frame, and track 16 mounted on the door itself. In any event,
rotation of
pinion 20 on door closer housing 12 transmits door motion between the door
closer housing and either the door or door frame, depending where the door
closer
is mounted.
During the door opening, the door closer has an otherwise conventional
mechanical spring to store potential energy to provide a bias to swing the
door
closed. This is shown in the interior view of door closer 10 in Figs. 3 and 4,
where
coil spring 40 has a central opening along its longitudinal axis and extends
around
the outside of sleeve 44 which has an open end 42 secured within the door
closer
housing 12. Spring 40 is normally in an extended position, and is able to
compress
along its longitudinal axis. Spring end 40a is secured to sleeve end 42 and
has an
opposite end 40b that is moveable toward and away from end 40a to increase and
decrease, respectively, the degree of compression of the spring, i.e., the
spring
deflection. Pinion 20 is mounted to rotating member 22, and both rotate about
pinion axis 21 with respect to housing 12. To compress spring 40 as the door
opens, a cam 30 within member 22 engages an elongated connecting member 60
attached adjacent distal spring end 40b to cause spring 40 to compress as
pinion
20. Connecting member 60 extends through the length of sleeve 44 and coil
spring
40 to a position beyond spring end 40a where the connecting member is
tangential
to and engages the peripheral edge of the cam. In the embodiment shown in
Figs.
3 and 4, connecting member 60 is a flexible, but non-stretchable steel fiber
cable
that has one end secured by tab 62 at a position on the periphery 32 of cam
30.
The other end of the cable is secured by tab 64 within an opening in cap 46 at
the
end of spring 40. As the door is urged to an open position, pinion 20 and cam
30
rotate in a counterclockwise direction of arrow 24 as shown in Fig. 3, and
cable 60
is wrapped within groove 34 extending around the periphery 32 of the cam,
which
acts as a pulley. As cable 60 pulls to the left, movement of tab 64 at the
opposite
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end of spring 40 causes cap 46 to compress spring 40 on sleeve 44, and imparts
an
increasing tensile force transmitted along the longitudinal axis of cable 60
as a
result of increasing degree of compression of the spring. The length of the
cable 60
engaged from the starting position, when the door is beginning to open, to the
final
position, when the door is fully opened, is the distance of compression of
spring
44. The linear spring and pinion provide an opposing torque about the pinion
axis
of rotation as the door is opened and subsequently uses the potential energy
stored
in the spring to close the door once the user has released the door. Once the
open
door is released, the spring expands causing cable 60 to rotate pinion 20 and
cam
30 in the opposite, clockwise direction of arrow 24 as the cable unwraps and
impart force through arm 14 to close the door. Spring 40 exerts a varying
force on
connecting member 60, depending on spring end 40b position and the degree of
spring compression, according to the spring constant.
In order to compensate for the spring force variation, the configuration of
periphery
32 of cam 30 is non-circular, and is designed to vary according to the force
imparted by spring 40 in any position of the spring. In the embodiment shown,
the
present invention provides a constant output torque from door closer/operator
10
which uses linear spring force to provide an output torque on pinion 20. Door
closer 10 has a rigid attachment from the door to the door closer pinion 20
that
causes a rotational motion on the pinion from a rotation of the door, and a
linear
spring 40 that is responsible for the force felt when opening the door due to
the
spring compression. In particular, the present invention changes the vector
displacement on the pinion from the spring force as the pinion rotates and the
spring compresses.
A modification of the cam is shown in Figs. 5 - 7, where cam 30' has a central
opening 35 for mounting on a shaft 23 of rotating member 22' (Fig. 5). Cam 30'
has
recess 33 in periphery 32 for receiving tab or pin 62 on the end of cable 60.
The
cam periphery 32 with the varying distance from cam axis 12 is along the
groove
34 which receives the cable as it wraps around the cam during rotation. A
bevel
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gear may be provided for attachment to a dampening or door motion control
component of the type conventionally used, for example, an electrical motor.
A constant force value for opening and closing the door may be predetermined
by
the user and/or the door requirements. The constant force value is typically
measured from a predetermined distance from the pivot point of the door. The
desired constant force value determines a specific torque on the pivot point
of the
door a user wishes to achieve.
Without the changing the cam radius, door closers using a single lever arm are
subject to increasing door opening and closing force as the angle of door
opening
increases. A door closer comprised of a spring having a linear increase in
spring
force and a circular groove periphery 32 of a fixed radius about pinion 20
results in
a linear increase in torque on the pinion as well, as shown in Fig. 8. In the
present
invention, the change in vector displacement to eliminate the increasing door
opening and closing force is accomplished by using a cam profile whereby the
radius on the cam changes with respect to the rotation of the pinion. More
specifically, the cam profile has a varying radial distance between the cam
axis of
rotation and the position that the connecting member is tangent to the
peripheral
edge of the cam. Fig. 9 shows an example of the variable radius cam pulley 30.
Tab or pin 62 on the end of cable 60 is inserted in a groove on the pulley.
Cable
position 60a represents the cable position with the door closed and at the
beginning of the door opening, where the cam has a radius or radial distance
Ro
between cam and pinion axis 21 and point To at which cable 60a is tangent to
cam
peripheral edge 32. Spring 44 is compressed minimally or not at all at cable
position 60a. As the door opens, and the pinion and pulley rotate, closer
spring 40
begins to compress, thereby producing a linear increase in force on cable 60.
The
radius on the cam at every degree difference from the initial cable position
60a, at 0
degrees, is calculated such that the radius decreases with respect to the
increase in
spring force, yielding a constant output torque on the pinion. As cam 30
rotates,
the radius changes, and the cable continues to compress the spring and
generating
a torque on pinion 20. The torque on pinion 20 is kept constant by varying the
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radius on the cam profile at each degree. As shown in Fig. 9, at cable
position 60b,
the cam has rotated 65 degrees and tangent point T65 has a radial distance of
R65
between axis 21 and T65 on periphery 32. Upon further rotation of the cam to a
total of 120 degrees, at cable position 60c, tangent point T120 has a radial
distance
of Rizo between axis 21 and T120 on periphery 32. The final cable position
60d,
with final radial distance R, may be at any desired tangent point T on the cam
periphery. At the final cable position, the total cam circumference of the cam
profile, i.e., the total peripheral distance from initial tangent point To, is
equal to the
total displacement of spring 44.
After selecting the desired output torque, one can then determine the radius
at each
degree for any selected spring stiffness. To calculate the pulley profile
necessary to
keep the torque constant, first determine with the spring constant or K value
of the
spring, the desired output torque T and an initial radius or radial distance
value
between the cam axis and the connecting member at the position tangent to the
cam
peripheral edge, which is a limit due to design. The desired tangential force
f acting
on the pulley at the initial radius is then calculated. With a known K value
the
preload necessary to acquire this initial force is known. The profile
calculation
method assumes that the radius remains the same between each degree of
rotation.
From this assumption the distance of spring displacement may be found from the
distance traveled around the cam periphery at a constant radius between
degrees of
cam rotation. The spring force at each degree of rotation may be determined by
adding the perimeter distance traveled per degree with the preload multiplying
by
the K value. Once the force at each degree is known, the radius necessary at
each
degree to provide a constant output torque may be found, as follows:
Initial radius of pulley at 00 = ro (fixed by pulley size limitation)
Initial force on spring = fo
Initial torque T on pulley = ro x fo (torque T will remain constant)
Radius of pulley at 10 rotation:
R1 =
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fl is measured by spring displacement calculated from radial distance traveled
by
pulley between 00 and 10, which is approximate since the radial distance
changes
slightly between 00 and 1
Radius of pulley at 2 rotation:
R2 = Tif2
f2 is measured by spring displacement calculated from radial distance traveled
by
pulley between 10 and 2
Radius of pulley at n rotation:
R,, ¨ T/f,,
f0 is measured by spring displacement calculated from radial distance traveled
by
pulley between n and (n +1)0
Calculation of force in a spring:
F = K (X - X0),
where: F = Force
K = Spring Constant
X = Distance from Equilibrium
X0 = Spring Equilibrium Position
Using the decreasing radius or radial distance from the cam axis to the cable
tangential point as the cam rotates as determined above, the torque on the
pinion,
or force felt opening the door, is constant across the angle on the door
opening as
shown in Fig. 10.
Instead of using a cable as the connecting member secured to the spring,
another
embodiment of the closer of the present invention includes a geared pinion, a
damping component, and a geared rack. The pinion diameter and rack thickness
change as the pinion gear teeth engage the rack teeth during compression of
the
spring. In such embodiment shown in Figs. 11 - 13, the cam 30" comprises an
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eccentric pinion gear with teeth 37a about the peripheral edge 32 that has the
desired profile and the connecting member 60" comprises a rack 65 at the end
engaging the pinion gear with correspondingly sized teeth 37b along a
correspondingly curved side thereof to engage the pinion teeth. As before with
cam
embodiment 30 and 30, cam 30" has a varying radius or radial distance R
between
the axis 21 and the point on the peripheral edge 32 that is tangent to or
engages the
teeth of rack 65 that is calculated at each degree of rotation from the
starting position
to produce a constant torque on the pinion as spring 44 is compressed by
connecting member 60". Since rack portion 65 at the end of connecting member
60" is rigid and cannot wrap around the cam as in the cable embodiment, the
thickness D of the rack at the point of contact with cam 30" changes from the
initial
position (Fig. 11) to the final position (Fig. 13).
Operation of cam 30" is similar to that of the preceding cam embodiments,
except
for the meshing of the gears between the pinion gear and the rack and the
inflexibility of the rack portion. In Fig. 11, at the starting position with
the door
closed, Ro is the radial distance between axis 21 and gear teeth 37a at the
cam
periphery 32 at the point of engaging and meshing with teeth 37b of rack
portion 65.
The position of cam 30" after rotation of 90 degrees is shown in Fig. 12, and
the
radial distance between the cam axis and the point of meshing with the rack
teeth is
R90. Because rack portion 65 is not flexible, the upper surface of the rack is
inclined
at an angle to have an increasing distance D above the level of engaged rack
teeth
37b in Fig. 11, and the sum of the length of D90 and R90 is substantially
equal to the
length of Ro. At the final position with the door fully opened, shown in Fig.
13, cam
30" rotated 180 degrees, and again the sum of cam radius R -180 and rack
height Diao
is Ro. The length of the teeth 37b engaged from the starting to the final
position is
the distance of compression of spring 44. The curved profile of rack portion
65 is
complimentary to the profile of cam 30" in that the height of rack 65 is
always the
difference between Ro and the radial distance between the cam axis and the
point of
engagement with the rack. Like the previous cam embodiments, the output torque
on the pinion is constant throughout the opening and closing of the door.
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While the rack acts as a piston for hydraulic damping in this embodiment
damping
components may alternately or further include an electric motor attached to
the
pinion, whereby the motor controls the motion and movement of the door to act
as a
door operator. All components attached to the pinion, such as an electric
motor,
.. experience a constant load during operation of the door closer/operator for
better
control and longer life. The constant output torque can further be adjusted to
meet
the application by pre-compression of the linear spring.
Included in the aforementioned embodiment of the pinion and connecting member
is an eccentric sprocket and flexible chain arrangement, where the cam is a
sprocket
with the configuration of the pinion with peripheral teeth, and the chain has
rollers
which serve and function as the teeth of the rack. Instead of being rigid like
the
rack, the connecting member chain is flexible and non-stretchable, similar to
the
cable. As the spring compresses, and the spring force increases, the pitch
diameter
on the sprocket pinion would decrease as with the aforedescribed cam
configurations to maintain a constant torque on the cam and pinion.
Instead of a non-circular peripheral edge, the cam may have a circular profile
with
the axis of rotation offset from the center of the circle, particularly if
approximating a
constant torque for less than the full degree of swing of the door. As an
alternative
to the constant force described above, the cam profile in the door closer of
the
present invention may be configured to provide a varying force during the
opening
or closing of the door at any or all positions. One skilled in the art will
appreciate
that the teachings herein would enable the cam profile to be modified to
provide
more or less than a constant force at any position of the door movement by
changing
the profile to increase or decrease the torque on the door closer pinion at a
desired
.. point or range of spring position.
In operation of the door closer or operator of the present invention, any of
the
aforedescribed cam and connecting member embodiments may be employed. With
such a door closer or operator, when starting in either the closed or open
position,
the user urges the door into the other of the open or closed position,
whereupon the
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pinion and connected cam about the cam axis rotate as the door moves. The
rotation of the cam causes a change in length of the portion of the connecting
member between the position tangent to the cam peripheral edge and the spring
second end to expand or compress the spring and transmitting a force along a
longitudinal axis of the connecting member as a result of degree of
compression of
the spring. The result is that a desired torque is maintained about the axis
of the cam
and the connected pinion as the door moves to the other of the open or closed
position.
The present invention can be used on any door within the limits of the
.. closer/operator design. The shape of the cam may be determined by variables
such
as spring linearity, pivot locations, door resistance, desired movement of the
door,
and track forces whether or not the arm is connected directly to the door or
doorframe.
Instead of having one linkage arm with sliding track configuration, the door
closer
of the present invention may be used in door closing systems which include a
two
linkage arms connected in series (also known as a double lever arm) from the
door
closer to the door or frame, depending where the door closer is mounted. Fig.
14
shows door closer 10 mounted on the upper face of a door 90 with a double
lever
arm for pivoting the door between open and closed position. The double lever
arm
.. is made up of linkage arms 14 and 15 pivoting about pin 17 at arm ends 14b
and
15a. Arm 15 is connected at end 15a by pin 19 to a bracket 18 on door frame
80,
and arm 14 is connected at end 14a to pinion 20 and is rotatable therewith.
The
opposite mounting may be used, with door closer 10 mounted to frame 80 and
bracket 18 mounted on door 90. The present invention may also be used on door
.. closers in which no linkage arms are used, where the door is secured to the
pinion
such that the axis of rotation of the door becomes the axis of rotation of the
pinion.
In Fig. 15 such an arrangement is shown in which door closer 10 is attached to
door 90, and pinion 20 acts as the hinge on which the door swings.
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With a constant torque output, the rigid arm and track assembly can be used on
ADA required doors giving the clean look of a track setup with the performance
of a
double lever arm. This design can also be useful in applications where a
double
lever arm cannot be used due to safety issues (mental health facilities,
prisons, etc.)
but the user has the need for a constant force on the door. The benefits of
the cable
cam design over the standard roller/cam design are the less strict tolerances
and the
elimination of wear components such as bearings in the roller.
While the present invention has been particularly described, in conjunction
with a
specific preferred embodiment, it is evident that many alternatives,
modifications
and variations will be apparent to those skilled in the art in light of the
foregoing
description. It is therefore contemplated that the appended claims will
embrace
any such alternatives, modifications and variations as falling within the true
scope
and spirit of the present invention.
Thus, having described the invention, what is claimed is:
